Skin barriers are commonly used with ostomy appliances to seal the faceplates of such appliances against peristomal skin surfaces and thereby protect those surfaces from exposure to stomal effluent as well as to prevent leakage of such effluent from about the stoma-receiving openings of the pouches. Such barrier rings are usually available as integrated elements of ostomy appliances, being included as part of the adhesive faceplate of such an appliance as shown, for example, in U.S. Pat. Nos. 4,973,323; 4,834,731 and 4,710,182.
Skin barrier compositions for ostomy use should have certain physical properties, some of which have been well recognized in the past and others of which are believed now to have been discovered, or at least fully recognized, in conjunction with this invention. It has been known, for example, that barrier materials should be skin-friendly, that is, they should be soft, flexible and non-irritating to the skin and be capable of expanding and contracting in accord with body movements. They must remain adherent to the skin for extended periods but the adherence must not be so aggressive as to risk skin injury or irritation during use and upon barrier removal. A skin barrier composition should have sufficiently high cohesive strength to resist disintegration throughout its duration of use and to remain intact at the time of removal so that little or no residue remains adhered to the skin. While prior skin barrier compositions are known to achieve some of these objectives, they are also known to fall short in meeting others, particularly with respect to providing controlled hydration and sufficient strength when saturated.
Skin barrier compositions typically contain hydrocolloid particles dispersed throughout a continuous elastomeric adhesive phase. Initial tack, usually referred as "dry tack," is provided by the continuous phase but, because such a barrier is occlusive or non-breathable, adherence to the skin would be disrupted by perspiration and by liquid stomal discharge if it were not for the dispersed hydrocolloids which absorb fluids and thereby maintain and possibly enhance adhesive attachment to the skin. U.S. Pat. No. 4,551,490 and other references disclose that suitable water-absorbing and swellable hydrocolloids gums include sodium carboxymethylcellulose, pectin, gelatin, guar gum, locust bean gum, gum karaya, and mixtures thereof. The elastomers used in the continuous phase of the '490 patent are low molecular weight polyisobutylenes (having a viscosity average molecular weight from about 36,000 to about 58,000) with which butyl rubber (having a viscosity average molecular weight from about 350,000 to about 450,000) may be blended. The patentees also disclose that the elastomeric phase may contain a styrene block copolymer component to help provide extensibility and recovery from modular strains to the composition. In addition, such a composition may include mineral oil, to increase stretchability and adhesiveness of the blend, and a suitable tackifying agent and antioxidant.
A commercial skin barrier composition believed to be made in accordance with the teachings of the '490 patent is now recognized as having certain properties that compromise its usefulness as a barrier material for ostomy appliances, particularly those intended for urostomy and ileostomy use. In such an appliance, the barrier ring has an inner margin exposed to liquids discharged from the stoma into the collection pouch, resulting in liquid absorption and swelling of barrier's hydrocolloid content especially along that margin. Because of its relatively high rate of absorption, the barrier along at least a portion of the inner margin becomes saturated and the saturation front advances outwardly towards the outer margin of the barrier ring, sometimes reaching the outer margin after only a relatively short wearing interval of two days or less. Once the saturation front reaches the outer margin, leakage occurs and the faceplate (or the entire appliance if it is a one-piece appliance) must be replaced.
It is also been found that because saturation greatly reduces the cohesive strength of such a barrier material, great care must be exercised in the removal of such an appliance if tearing of the barrier ring or annular wafer is to be avoided. Should tearing occur, one particular constituent of the composition which is known to become odoriferous upon prolonged hydration becomes more exposed and particularly strong and objectionable odors are released. More serious is the fact that tearing often results in at least partial disintegration of the barrier with a portion of the ring remaining as a residue on the skin. Removal of the residue with alcohol or other solvent is not only an inconvenience but may result in irritation of the sensitive stomal and peristomal surfaces. Unfortunately, the risk of tearing is enhanced by the combination of strong wet tack of the barrier material and its and relatively low cohesive strength when saturated. Should the saturated barrier material along the inner margin of the faceplate swell into contact with the pouch or the pouch coupling ring of a two-piece appliance, then tearing of the barrier material might easily occur simply by uncoupling the pouch component. A user desiring simply to replace a pouch and having no intention of also removing the faceplate from its adhesive attachment to his/her body may suddenly find such faceplate removal is necessitated by the swelling, adhesion, and unavoidable tearing or disintegration of the skin barrier ring.
Other patents illustrative of the state of the art are U.S. Pat. Nos. 4,166,051, 4,204,540, 4,231,369, 3,339,546, 5,059,189, 4,393,080, 4,192,785, 4,743,499, and 4,181,635.
Important aspects of this invention lie in recognizing the deficencies of prior barrier compositions for ostomy use, particularly urostomy and ileostomy use, and discovering that such deficiencies may be overcome by completely avoiding the use of low molecular weight polyisobutylene and by formulating an adhesive barrier composition with an elastomer blend composed substantially entirely of one or more high molecular weight polyisobutylenes and one or more styrene block copolymers. Specifically, the polyisobutylene or polyisobutylenes in the elastomer blend should have a viscosity average molecular weight within the range of about 750,000 to 2,350,000, a preferred range being about 1,000,000 to 1,900,000. On a percentage weight basis with respect to the composition as a whole, the elastomer blend constitutes less than 25 percent of the composition with the high molecular weight polyisobutylene(s) falling within the range of about 2 to 15 percent and the styrene block copolymer(s) constituting about 5 to 20 percent. Also included in the adhesive composition is a plasticizer of either petrolatum or mineral oil (6 to 20 percent) with petrolatum being preferred. The composition additionally includes about 10 to 35 percent tackifier and up to about one percent antioxidant. The water-absorbing and swellable hydrocolloids constitute about 35 to 65 percent of the composition and are selected from the group consisting essentially of sodium carboxymethylcellulose and pectin, or mixtures thereof, and optionally include minor amounts of other hydrocolloid gums. The inclusion of gelatin is preferably avoided.
An ostomy skin barrier composition of this invention, and wafers or faceplates for ostomy appliances utilizing such composition, are noteworthy for their durability and other physical properties under real and simulated conditions of use. The weartime of a faceplate utilizing the skin barrier composition of this invention may be eight days or more, far exceeding the weartime of appliances utilizing prior barrier compositions. Such extended weartime results in part from the fact that hydration occurs more slowly and in a controlled manner, with such hydration resulting in the absorption of perspiration, with the appliance therefore remaining effectively adhered to the skin, but with the saturation front that migrates outwardly from the inner margin of the annular barrier advancing too slowly to reach the outer margin and cause leakage under normal conditions and periods of use. Even when hydrated, the composition is relatively strong and resists tearing, so that such a barrier may be more easily removed intact, without portions or fragments clinging to the skin, following extended periods of wear. When the composition is used as the barrier material for a two-piece appliance, the problems encountered in the past, in which the formation of a "turtleneck" of swollen barrier material at the inner margin of a faceplate adheres to the pouch (or pouch ring) so to become torn and require faceplate removal when a pouch is uncoupled for replacement, are eliminated or greatly reduced. Even if the skin barrier should somehow become torn following hydration, substantially less objectionable odor escapes because of the barrier formulation and, in particular, because of the absence of significant amounts of gelatin in that composition.
Other features, advantages and objects of the invention will become apparent from the specification.